Our aim is to characterize the mechanics of DNA replication in chromosomes and extra-chromosomal elements. We use bacterial and yeast plasmids as simple experimental systems before moving to YACs (Yeast Artificial Chromosomes) and the complex chromosomes of higher eukaryotes. Our interest is not focussed only in the identification of origins, replication fork barriers and termini, but also in the topological changes that occur during DNA replication. In this way we hope to improve our knowledge on the structure and function of eukaryotic chromosomes. Our long-term goal is to build up artificial chromosomes that might be used as stable vectors to transform plant and mammalian cells in order to allow gene therapy in these organisms. To know more about our latter achievements in this field click here.